It's usually almost exactly the amount of sugar that is not cacao if you look at the label. Milk chocolate is like over half sugar by weight.
There sad reality is that cacao is extremely bitter, so every gram of sugar is sorely needed to balance it out. I've settled on 70% cacao (so like 29% sugar) as a good balance of being dark for the endorphins and still enjoyable to even eat. Over 90% it stops even being the consistency of chocolate and starts to approach something resembling a brick of raw cocoa.
There sad reality is that cacao is extremely bitter, so every gram of sugar is sorely needed to balance it out. I've settled on 70% cacao (so like 29% sugar) as a good balance of being dark for the endorphins and still enjoyable to even eat. Over 90% it stops even being the consistency of chocolate and starts to approach something resembling a brick of raw cocoa.